1. Field of the Invention
The present invention relates to handles for hand-held tools, such as hammer drills, and in particular to handles that can be removably mounted to hand-held tools.
2. Description of the Related Art
In the case of a known hammer drill that has a relatively large size and is designed to be held with both hands of an operator during the operation, an auxiliary handle is provided in addition to a main handle. Therefore, the operator can grasp the main handle with one hand and can grasp the auxiliary handle with the other hand. In general, such an auxiliary handle is provided as an optional component and can be mounted to and removed from the tool. Two different types of auxiliary handles are generally used for different modes of operations. One type is a bar-type handle that has a grip portion extending laterally from the tool. The other type is a D-shaped handle that has a pair of support arms and a grip portion extending between the support arms. The support arms extend laterally from the tool and are spaced from each other by a predetermined distance. The bar-type handle is suitable to handle-held tools that may receive a rotational torque (e.g., about an axis of a tool bit) from a workpiece during the operation. The D-shaped handle is suitable to hand-held tools that may receive vibrations in the vertical direction (e.g., due to a reaction force applied to a tool bit in an axial direction) from a workpiece during the operation.
Japanese Laid-Open Publication No. 2000-176864 teaches a known D-shaped auxiliary handle as shown in FIG. 11, which corresponds to FIG. 1 of this publication. Referring to FIG. 11, an auxiliary handle 10 has a clamp portion 11 for clamping a front case 2 of a hand-held tool 1, an operation device 12 for operating the clamp portion 11, and a grip portion 13 adapted to be grasped by the operator. The clamp portion 11 has a pair of clamp halves 11a that can clamp the front case 2 therebetween from opposite sides. The front case 2 has a substantially cylindrical tubular configuration. The clamp halves 11a are held in the clamping position by tightening a fixing nut 12a of the operation device 12. The clamp portion 11 can be removed from the front case 2 by loosening the fixing nut 12a, so that the auxiliary handle 10 can be removed from the hand-held tool 1.
Referring again to FIG. 11, a main handle 3 is disposed on the rear end (right end as viewed in FIG. 11) of the hand-held tool 1. In order to operate the tool 1, the operator can grasp the main handle 3 with one hand and can grasp the grip portion 13 of the auxiliary handle 10 with the other hand, so that the operator can hold the tool 1 with both hands.
However, with the above known auxiliary handle 10, the support arms 14 and 15 extend laterally from opposite ends in the vertical direction of the support portion 12, and the grip portion 13 is fixed to the tip ends of the support arms 14 and 15 and extends therebetween. In addition, as the fixing nut 12a is tightened, the support arms 14 and 15 may be flexed toward each other, so that the clamp halves 11a of the clamp portion 11 can clamp the hand-held tool 1. Therefore, the tolerance of the opening and closing movement of the clamp halves 11a of the clamp portion 11 given by the operation of the operation device 12 (i.e., the tolerance of the flexing amount of the support arms 14 and 15) is not sufficient. Practically, the clamp halves 11a of the clamp portion 11 cannot be largely opened relative to the front case 2 of the hand-held tool 1 unless the auxiliary handle 10 is disassembled. Therefore, the mounting and removing operations of the auxiliary handle 10 is troublesome and require much time.
In addition, due to the small tolerance of the opening and closing movement of the clamp halves 11a, the sizes of hand-held tools, to which the auxiliary handle 10 can be mounted, are limited within a narrow range.
Therefore, there has been a need for handles that can be easily mounted to and removed from hand-held tools and are improved in versatility.